Method of removing gases from metals



Patented Mar. 10, 1931 JULIUS VON BOSSE, OF'BOMTZ- BERG, NEAR LEIPZIG, GERMANY HIETHGD F REMQVING GASES FROM METALS Ito Drawing. Application filed March 531, 1927, Serial No. 180,081, and in Germany March 7, 1&2?

Many metals absorb gases during their preparation either by occlusionor by forming unstable compounds which have a detrimental effect upon the properties of the metals. Thus, for instance, most of the metal coatings produced electrolytically contain I large quantities of hydrogen which renders the metal coating brittle and as the hydrogen is gradually liberated blisters are formed which cause the coating to peel 0d.

The removal of such gases from metals has hitherto been possible only by increasing the temperature of the metals sometimes until they became incandenscent. The metals were, however, detrimentally affected by such a treatment, as regards both their appearance and their whole structure. In the case of galvanic deposition, the heating sometimes even caused the supporting metal to I have found that it is possible to remove gases from metals which have absorbed them without subjecting the metalsto a substantially increased temperature, by making the metals electrodes in an evacuated space thatis, a vacuum tub and applyin thereto a voltage of a few hundred or a w thousand volts. As soon. as the current is switched on, the metal objects which are mounted in the rarefied space or tube begin to liberate the occluded or otherwise retained particles of gas, which is shown by an increase in the pressure of the gas within the vacuum vessel. In this way it is possible to completely remove the gas within a few minutes or a few hours according to the thickness of the metal or metalsupport which is subjected to treatment. It is quite immaterial as to how far the gas has penetrated into the 4 metal. Oorroded objects of galvanically formed metal can be completely freed of the absorbed gases by the process according to the present-invention.

Use maybe made alternating current; however,

either of direct or of when direct trodes current is used, only the cathode liberates gas, whilst with alternating current the gas is liberated .from both electrodes. The heat produced during the process causes the liberation of gas to be uniformly accelerated, whereby the duration of the treatment is substantially shortened. Nevertheless, the amount of heat produced is so small that the temperature of the metals acting as elecdoes not exceed 100 C. so that a 5 change in the metal itself does not take place.

In the case of thin metal layers the removal of the gas is efi'ected in a comparatively rapid manner and is terminated, as is also the case in the case of, metals which with the voltage used are already undergoing electrode disintegration, before any alteration is visible on the surface by distintegration of metal. Thus for instance shiny guilded metal ob- 'ects can be freed of gas without the lustre of the surface being thereby in any way affected.

As the gas is liberated,-the metal is at the same time cleaned since the mechanical impurities adhering ,to the surface as well as m the small quantities of oxide that are present are simultaneously removed. In this we it is for instance possible to remove oxide pel icles from aluminium and thereupon galvanically cover the aluminium with a more 7 metal or permanently lacquer it.

treatment is continued suiliciently long by using suitable voltages metal coatings of other metals can be again removed. Thus for instance the process may advantageously 30 be employed in connection with waste rolled gold which may be rendered suitable for reuse without it being necessary to melt it down. If waste rolled gold is used as an electrode in the process according to the pres- 5 cut invention, the gold coating is *dislntegrated in the form of dust which is collected, leaving behind the plate of tombac which serves as a support.

precious If the Having now particularly described and as- 00 certained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is A method of freein electrolytically deposited metal coatings om absorbed hydrogen gas contained therein and which impart embrittlemcnt characteristics thereto, which comprises subjecting the metal coating to be treated to an-electric discharge in a vacuum tube, the metal coating forming one of the electrodes in said tube.

In testimony whereof I have signed my name to this specification.

JULIUS v. BOSSE. 

